Session F02: Virtual Poster Session (4:00pm-6:00pm, PT)

Introducing the sub-photon as a basis of the structure of photons

Considering that the smallest, fastest, and lightest object in the universe is photon and the universe mass is about  10⁵³  kg, if we consider the photon as the basis of the Big Bang, the volume and density are far different from the information that obtained for the Big Bang before. In other words, the photon is not the desired particle that could have formed the Big Bang sphere. Therefore, we define a special particle called "sub-photon" with dimensions of one billionth of a photon (in terms of radius value). In this paper we will show that this fundamental particle could be the basis of the structure of photons   

One-dimensional dipole-octopole or dipole-octupole interactions

Very similar to van der Waals interactions or dipole-dipole interactions, the lowest-order multipole-multipole interactions among neutral atoms, dipole-octopole interactions are one type of higher-order interactions among neutral atoms. Some literatures use octupole, and others use octupole. In this presentation, we will use octopole. Here we consider dipole-octopole interactions among highly excited atoms or Rydberg atoms. One Rydberg atom has one ion core and one highly excited atom, or a positive and negative pole of a dipole. Therefore, a Rydberg atom can be treated as an electric dipole. Quantum mechanically, Rydberg atoms have octopole moments, so Rydberg atoms can also be treated as an octopole. Hence, Rydberg atom-atom interactions can be treated as dipole-octopole interactions. In this presentation, few-body dipole-octopole interactions will be investigated. There are many applications. For example, such interactions are essential for creating more compact quantum computers, quantum devices, and quantum electronics.

    

Quadrupole effects in the photoionization of sodium 3s in the vicinity of dipole Cooper minimum

We present a study on the impact of quadrupole transitions on the asymmetry parameter  for the 3s photoionization of Na atom. The nondipole parameters are derived from the general formulation of angular distribution of photoelectrons developed by Keh-Ning Huang (KH) [1], which is based on Jacob and Wick's helicity formulation [2]. The required transition amplitudes for these calculations are obtained from RATIP [3], which is based on KH formulation. The wavefunctions of the initial and ionized state of the system are obtained from GRASP [4]. We compare and contrast Johnson, Lin [5] and Derevianko et.al’s [6] formulation with that of KH formulation and show that for closed shell atoms the two formulations are equivalent. [1] Huang, K. N. Phys. Rev. A 1980, 22, 223. [2] Jacob, M., Wick, G. C. Ann. Physics 1959, 7, 404. [3] S. Fritzsche, Comput. Phy.s Commun. 2012, 183, 525. [4] Parpia F. A., Fischer C. Froese, and Grant I. P., Comput. Phy.s Commun. 1996, 94, 249. [5] Johnson W. R. and Lin C. D. Phys. Rev. A 1979, 20, 964. [6] Derevianko A., Johnson W. R. and Cheng K. T., ADND, 1999, 73, 153.   

Interplay between electronic and nuclear charge in the photoionization of x@C60 with x = Cu+, Cu, Cu–, Zn

A computational study of the photoionization of atomic outer s and d subshells of endofullerene molecules, such as, the neutral Cu@C₆₀ and Zn@C₆₀ and the ionic Cu⁺@C₆₀ and Cu^–@C₆₀ is carried out.  The ground states of the systems are described by density functional theory (DFT) with C₆₀ positive ion-core modeled in a jellium frame. The photoionization is calculated in a linear-response time-dependent DFT framework [1]. The LB94 exchange-correlation functional [2] is employed. Ground state and ionization properties of the outer 4s state are found qualitatively similar among Cu@C₆₀, Cu^–@C₆₀ and Zn@C₆₀. However, for the inner 3d state, even though the properties are found similar within each pair of [Cu@C₆₀, Cu^–@C₆₀] and [Cu⁺@C₆₀, Zn@C₆₀], they are very different from one pair to another.  Thus, for 3d, it appears that the nuclear charge of the central species is playing a role in combination with the electronic charge. [1] J. Choi et al., Phys. Rev. A 95, 023404 (2017); [2] R. van Leeuwen and E. J. Baerends, Phys. Rev. A 49, 2421 (1994).   

Transition amplitudes in length and velocity forms in the photoionization of intermediate subshells of high Z atoms

Chandrasekar's work is one of the earliest in which photoabsorption matrix elements were determined in length, velocity, and acceleration forms [1]. Out of the three forms, the length and velocity form calculations are commonly discussed [2–4]. Non-local potentials typically cause non-equivalence of length and velocity forms [5]. Relativistic and correlation effects also play important roles in the inequality of length and velocity forms [4]. In the present work, we attempt to identify the conditions, causes, and consequences for the non-equivalence between length and velocity forms of transition matrix elements in the intermediate subshells of atomic mercury. The matrix elements are calculated using the RRPA [6] and the RRPA-R [7]. Truncation of the RRPA impacts the equivalence of the different gauges, but to varied extents in different energy regions. [1] S. Chandrasekhar, Astrophys. J. 102, 223 (1945). [2] A. F. Starace, Phys. Rev. A 3, 1242 (1971). [3] I. M. Savukov and W. R. Johnson, Phys. Rev. A 62, 052506 (2000). [4] G. Aarthi et al., J. Phys. B 47, 025004 (2014). [5] I. P. Grant, J. Phys. B 7, 1458 (1974). [6] W. R. Johnson and C. D. Lin. Phys. Rev. A 20, 964 (1979). [7] V. Radojevic, et al., Phys. Rev. A 40, 727 (1989).   

The Iron Project & The Opacity Project: i) Radiative data for the solar iron opacity, ii) Cl II-III spectra

From the on-going progress report of the radiative processes, particularly photoionization, for the 3 iron ions, Fe~XVII-XIX, dominant at the boundary of the convection and radiative zones (BCZ) inside the Sun where the plasma temperature is $2.11 imes 10^6$K and the electron density is $3.1 imes 10^{22}$cc the atomic data have now been implemented for determination of solar iron opacity at BCZ. Prelimiary results on opacity will be presented at the meeting. In this report an overall summany will be given of the radiative data for bound-bound transitions, the number of energy levels (with $nleq$10 and $lleq$9) and photoionization cross sections of these levels, of these ions that were needed for the opacity calculations. Features of photoinization depends on the state of the ion, such as, ground state, equivalent electron states, low and high energy states. Comparision of features of photoionization of the 3 Fe ions will be illustrated in order to understand the impact of them on the photoabsorption of the ions in determination of the opacity. The present work also reports, as part of work under the Iron Project, the predicted spectra of Cl II and Cl III that can assist in searching the signals of these ions in astrophysical spectra. The oscillator strengths for the bound-bound transitions in these two ions have been obtained in the relativistic Breit-Pauli R-matrix method.   

Development of a Rydberg Atom-Based Apparatus for Tracking Charged Particles

Rydberg atoms, with their high polarizability, are ideal candidates for detecting weak electric fields from charged particles. We have built a prototype apparatus to track an electron beam emitted from a 20 KeV thermionic electron gun using Rydberg Electromagnetically Induced Transparency (EIT) signal. The principle of the operation is to use the Stark shift in Rydberg atoms to detect the electric field of an electron beam passing through an atomic vapor. In the long term, we plan to implement our detection scheme with a high-energy electron beamline at Jefferson laboratory to detect relativistic electron beams.   

Formation of antihydrogen molecular ions by associative ionization

In this work, we present rates for the formation of the antihydrogen molecular anion by associative ionization (AI), as well as for the competing Penning ionization (PI) process, in low-energy collisions between spin-polarized metastable antihydrogen atoms.

These calculations were motivated by a recent study [Zammit et al., Phys. Rev. A. 100, 042709 (2019)] that proposed an experimental scheme by which antihydrogen molecular ions could be produced by laser excitation of metastable antihydrogen atoms held in a magnetic trap. Calculations were performed for temperatures less than 1 K, and high-energy fitting formulas were used to estimate rates at the low energies required for the experiment. It was predicted that at lower energies AI would have a higher rate than PI.

The present work extends the previous study by performing scattering calculations that incorporate fine structure and Lamb shift at lower energies (<10^-7 E_h). The resulting rates are compared with those extrapolated from high-energy fitting formulas. The low-energy behavior differs from what was predicted from the high-energy fits, with PI being the dominant ionization process at all temperatures. The relative efficiency, however, is within a factor of three at temperatures required by the experimental scheme.

    

Analytical pulse design for controlling the vibrational dynamics of polar diatomic molecules

Based on the idea of reverse engineering, we present an analytical pulse design protocol for controlling the vibrational dynamics of polar diatomics in a given electronic state. Using the appropriately shaped midinfrared laser pulse, the potential energy function is altered via the electric permanent dipole moment such that the molecule is driven along the user-defined quantum pathway. The proposed control is validated by accurately solving the time-dependent Schrodinger equation of the HeH+ molecular ion with two completely different methods. We find that besides smooth transitions, arbitrary Rabi oscillations as well as vibrational ladder climbing can be efficiently controlled with the present scheme. As a result, the molecule is successively excited beyond the potential barrier, leading to enhanced dissociation in the ground electronic state (Phys. Rev. A 106, 043113, 2022).   

Ballistic or statistic - The few-femtosecond dissociative dynamics of a bifurcating Jahn-Teller system

Jahn-Teller (JT) systems are particularly attractive for ultrafast spectroscopy, as the JT-induced symmetry breaking leads to significant changes in the observables of the system, allowing for the results of the relaxation to be easily measured and interpreted. Highly symmetric systems can have multiple JT-active modes, which can result in bifurcating relaxation pathways. Few JT systems, however, have been measured on the few-femtosecond timescale that their relaxation occur on.

Photoionised tetrahedral silane (SiH₄) is an example of such a highly symmetric and unstable system, known to fragment into SiH₂⁺ and SiH₃⁺, . Thanks to the unprecedented time-resolution offered by Soft X-Ray (SXR) attosecond transient absorption spectroscopy (ATAS) we are able to capture the short-lived transient species involved in the JT fragmentation of SiH₄⁺ and for the first time untangle the competing dynamics that lead to the distinct fragments.

Our ATAS results show that bifurcation in the dynamics occurs immediately after ionisation. The SiH₃⁺ fragment is created as a result of the T₂×t₂ JT effect within 30 fs of ionisation through a strong activation of the ν₄ asymmetric bending mode. This dissociation is found to be ballistic; it proceeds without a barrier and creates vibrational coherence in the fragment which we experimentally observe. This wavepacket in the umbrella mode is found to dephase within 100 fs due to the large amplitude of the vibration.

The dynamics of the SiH₂⁺ dissociation are found to be the strikingly different. For this pathway, the initial motion of the system is driven by the T₂×e JT effect, bringing it into a local D_2d minimum along the ν₂ scissoring mode. We are able to experimentally identify the spectroscopic signature of this transient species through its vibrational quantum beats, and find that it is only able to dissociate further into the SiH₂⁺ fragment through the anharmonic transfer of vibrational energy from the e mode into the t₂ modes. This process occurs statistically, resulting in a loss of vibrational coherence and the negative exponential rise of the SiH₂⁺ fragment’s spectral signature with a 155 fs timescale.   

Electromagnetically induced transparency in cesium

A ladder-type electromagnetically induced transparency (EIT) is investigated in cesium gas. We use two homemade external-cavity diode lasers (ECDL) to produce a weak probe beam at 852.3 nm (6S_1/2 → 6P_3/2) and a strong coupling beam at 520.3 nm (6P_3/2 → 18D_5/2). Results are compared with the theoretical predictions. This experiment has the potential to develop an advanced undergraduate laboratory in quantum optics using similar equipment used in traditional absorption spectroscopy.   

Generation of two-color correlated photon pairs at telecom wavelength from a warm atomic vapor cell

Quantum light sources in the telecom band are key components for long-distance quantum communication technology. We report a high-performance telecom-wavelength bi-photon source from a hot 87Rb atomic vapor cell. The time-correlated photon pairs are generated from the cascade-type 5S1/2–5P3/2–4D5/2 transition of 87Rb via the spontaneous four-wave mixing process. Under the condition of a high optical depth of 112(3) including the two-photon absorption with a spectral width of 260 MHz, we measure the maximum normalized cross-correlation value of 44(3) with a weak pump power of 2 μW and the full width at half maximum of cross-correlation function of 0.56(4) ns. We obtained the violation of the Cauchy-Schwarz inequality by a factor of more than 650. The high generation rate of the photon pairs is estimated as 108-order cps/mW. Furthermore, according to theoretical analysis from the 4-level atomic configuration, we examine the bi-photon spectral waveform (based on a stimulated emission tomography) and temporal waveform (based on cross-correlation function) of our photon pair source and confirm that the biphoton waveforms of photon pairs generated from the cascade-type transition are significantly affected by wavelengths difference between the lower and upper transition of the three-level atomic cascade system. We believe that our telecom-wavelength bi-photon source from an atomic vapor cell has useful in the application of long-distance quantum networks and in the context of realizing practical quantum repeater based on atom–photon interactions.   

Pump-Probe Cavity Optomechanics with a Rotating Atomic Superfluid in a Ring

Atomic superfluids confined in a ring provide a remarkable platform to study a plethora of phenomenona associated with quantum circulation. Recently, a versatile technique based on cavity optomechanics has been proposed¹ for real-time sensing and manipulation of atomic persistent currents with minimal destruction, and in situ. Here, we utilize this system to explore the coherent interference effects created by a strong control beam². We study the influence of an atomic persistent current on the transmission spectrum of a weak probe laser in a cavity containing bosonic ring condensate. For instance, at resonance the atomic circulation produces a double-optomechanically induced transparency which can be used to find the magnitude of the winding number. However, for non-resonant conditions, probe transmission shows Fano resonances. Furthermore, we find a switching from slow to fast light caused by atomic circulation. Our results may be used for sensing, state-transfer protocols, and optical switches.

1. P. Kumar et.al., Phys. Rev. Lett. 127, 113601 (2021).

2. S. Kalita et.al., Phys. Rev. A 107, 013525 (2023).   

Q-switching of an optical tweezer phonon laser

The demonstration of an optical tweezer phonon laser, which is an analog of optical lasers, has opened up a new path for the exploration of coherent dynamics in the levitated nanoparticle system [1].

So, towards this, we explore pulsed phonon lasing based on active Q-switching of a two-mode coupled levitated system [2]. The mode coupling is initiated between the two transverse oscillation modes of the trapped nanoparticle by periodically modulating the trap potential in the transverse direction. We find that when one of the modes is in a lasing mode, then in presence of time-dependent coupling, the second mode (non-lasing), also starts to exhibit pulsed lasing action, the properties of which can be controlled by tuning the parameters of time-dependent coupling. Our work on pulsed lasing can have applications in acoustic imaging, levitated phonon transport, and information processing.

References:-

1. R. M. Pettit et al, Nat. Photonics 13, 402 (2019).

2. Kewen Xiao et al, J. Phys. B: At. Mol. Opt. Phys. 55, 245401 (2022)   

CNN-LSTM neural network for high-fidelity, short-time state measurement and calculation of its cutoff detection time based on Jasen-Shannon divergence

  Fast and highly-accurate state measurements play an imperative role in quantum information technology. The state measurement of ion-trap-based qubits is performed by measuring photons from state-dependent scattering. The measurement fidelity is limited by the off-resonant transition during measurement and the imperfection of detectors such as dark counts. To address this problem, methods of utilizing time information of emitted photons have been studied to distinguish actual signals from false signals. It has been reported that the use of machine learning techniques can further improve the measurement fidelity since machine learning techniques can consider complex factors.

  In this paper, we propose a combination of convolutional neural network and long short-term memory (CNN-LSTM) model to improve the measurement fidelity. The model is designed to combine the strengths of each model. That is, CNN is specialized in capturing local features, and LSTM is specialized in processing sequential time information. The result shows that the combined model outperforms both CNN and LSTM models and it is robust to the size of time information.

  Moreover, we show that the amount of available information from the histograms of each state can be calculated based on Jasen-Shannon divergence. This calculated result can be exploited to determine the offset detection time and discard the redundant information, which in turn can save computational resources.   

High-fidelity two-photon geometric gates with a single-pulse Rydberg blockade scheme

Laser-excited Rydberg atoms provide controlled long-range interaction desired for atomic [1-5] and photonic [6-10] quantum technologies. In this talk, I present an approach to realize high fidelity CZ photonic gate by storing both control and target photons within an atomic ensemble [11] using non-Rydberg electromagnetically induced transparency (EIT) followed by a fast, single-step Rydberg excitation with global lasers. The proposed scheme [12] operates by relative intensity modulation of two lasers used in Rydberg excitation. Bypassing the conventional p-gap-p schemes [1,6,7], the operation features continuous laser shielding of the Rydberg atoms from the environment noise. The optical depth is optimized and the experiment is made simpler by the complete spatial overlap of stored photons inside the blockade radius. Here, a coherent operation is carried out in a region that was dissipative in earlier Rydberg photonic gates [6,7]. Encountering the primary sources of imperfection, this study comes to the conclusion that 99.7% fidelity can be achieved under realistic experimental conditions by taking into account the spontaneous emission of the Rydberg and intermediate levels, population rotation errors, Doppler broadening of the transition lines, storage/retrieval efficiency, and atomic thermal motion induced decoherence.

References:
1- M. Khazali, Klaus Mølmer, Phys. Rev. X 10, 021054 (2020).
2- M. Khazali, Quantum 6, 664 (2022).
3- M Khazali, Phys. Rev. Research 3, L032033 (2021)
4- M. Khazali, Phys. Rev. A 98, 043836 (2018)
5- M. Khazali, H. W. Lau, A. Humeniuk, C. Simon, Phys. Rev. A 94, 023408 (2016)
6- M. Khazali, K. Heshami, C. Simon, Phys. Rev. A 91, 030301 (2015)
7- M. Khazali, C. Murry, T. Pohl, Phys. Rev. Lett. 123, 113605 (2019)
8- M. Khazali, K. Heshami, C. Simon J. Phys. B, 50, 21 (2017)
9- M. Khazali, IJAP 10, 19 (2021)
10- Khazali, Mohammadsadegh. "Applications of Atomic Ensembles for Photonic Quantum Information Processing and Fundamental Tests of Quantum Physics." Ph.D. thesis, University of Calgary (2016).
11- H Kaviani, M Khazali, R Ghobadi, E Zahedinejad, K Heshami and C Simon, New J. Phys. 15, 085029 (2013)
12- Khazali, Mohammadsadegh. "All optical quantum information processing via a single-step Rydberg blockade gate." arXiv preprint arXiv:2211.06998 (2022).   

Progress Towards Multispecies Three-Node Quantum Network

Trapped ions are one of the leading platforms for quantum technologies including simulations, computing, sensing, metrology, and networking. Quantum networking enables scaling of ion-trap-based quantum computers, where individual ion chains in separate traps can be entangled via photonic interconnects. Here we report our progress towards a quantum network consisting of three multispecies ion traps in separate vacuum chambers. Each node of the network contains barium ions for remote entanglement generation and nearby ytterbium ions for quantum memory. Using different species avoids crosstalk between communication and memory qubits and allows us to benefit from individual strengths of each ion species. Barium is well-suited for communications since it emits single photons in the visible range of the electromagnetic spectrum. Ytterbium features long coherence times allowing for long-lasting quantum memory. This approach offers potential for the creation of larger quantum networks for quantum computing scaling, quantum communications and other applications of quantum technologies.   

Selective Field Ionization of Rydberg Atoms in a Vapor Cell

Rydberg atoms are natural radiation sensors due to their enhanced sensitivity to electric fields. Efforts are underway at the National Institute of Standards & Technology to use Rydberg atoms as calibration-free, SI-traceable sensors of thermal radiation, i.e., blackbody radiation (BBR), Rydberg atoms have the potential to characterize reference blackbodies at the 100 ppm level¹ or better, greatly reducing the calibration uncertainty for classical thermal radiation sensors.  To this end, a novel system has been developed to perform selective field ionization² (SFI) on Rydberg atoms in a vapor cell for population read out after BBR-induced state transfer.  SFI has previously been performed in a beam experiment³ or a magneto-optical trap⁴ where very good background pressures and electron multiplication techniques allow efficient detection of the liberated electrons.  Here, we discuss this new device which allows detection of field-ionized Rydberg atoms in a vapor cell without the aid of in-vacuum electronic multiplication. 

¹E.B. Norrgard, S.P. Eckel, C.L. Holloway, and E.L. Shirley.  New Journal of Physics 23, 033037 (2021).

²T. F. Gallagher, L. M. Humphrey, W. E. Cooke, R. M. Hill, and S. A. Edelstein.  Physical Review A 16, 1098 (1977).

³E. J. Galvez, J. R. Lewis, B. Chaudhuri, J. J. Rasweiler, H. Latvakoski, F. De Zela, E. Massoni, and H. Castillo.  Physical Review A 51, 4010 (1995).

⁴V. C. Gregoric, J. J. Bennett, B. R. Gualtieri, A. Kannad, Z. C. Liu, Z. A. Rowley, T. J. Carrol, and M. W. Noel.  Physical Review A 98, 063404 (2018).   

Ab initio - calculated streaked and angle-resolved direct and shake-up photoemission spectra for helium

Understanding the correlated ionization dynamics in atoms has remained a challenging

task. By implementing an adaptive FE-DVR method to efficiently solve the two-electron

time-dependent Schrödinger equation, we calculated ab initio attosecond time-resolved spectra for

streaked XUV photoemission from helium. For the n=2 shake-up channel, we find photoemission time-delays relative to direct photoemission in agreement with the experimental and calculated results of

M. Ossiander et al [Nature Phys 13, 280 (2017)] and provide relative photoemission delays for the n=3 shake up channel. Within a multipole expansion and by comparing our ab initio results for angle-resolved spectra with a simplified single-active-electron calculation, we examine the contributions of the lowest multipole orders of the residual He+(n=2,3) charge distributions on the photoemission delay.